check_cast_assign.c

   1 /*
   2  * Copyright (C) 2012 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "smatch.h"
  19 #include "smatch_extra.h"
  20 #include "smatch_slist.h"
  21
  22 static int my_id;
  23
  24 static struct symbol *get_cast_type(struct expression *expr)
  25 {
  26         if (!expr || expr->type != EXPR_PREOP || expr->op != '*')
  27                 return NULL;
  28         expr = strip_parens(expr->unop);
  29         if (expr->type != EXPR_CAST)
  30                 return NULL;
  31         return get_pointer_type(expr);
  32 }
  33
  34 static void match_overflow(struct expression *expr)
  35 {
  36         struct expression *ptr;
  37         struct symbol *type;
  38         int cast_size;
  39         int data_size;
  40
  41         type = get_cast_type(expr->left);
  42         if (!type)
  43                 return;
  44         cast_size = type_bytes(type);
  45
  46         ptr = strip_expr(expr->left->unop);
  47         data_size = get_array_size_bytes_min(ptr);
  48         if (data_size <= 0)
  49                 return;
  50         if (data_size >= cast_size)
  51                 return;
  52         sm_msg("warn: potential memory corrupting cast %d vs %d bytes",
  53                cast_size, data_size);
  54 }
  55
  56 void check_cast_assign(int id)
  57 {
  58         my_id = id;
  59         add_hook(&match_overflow, ASSIGNMENT_HOOK);
  60 }
  61